The number one use for a hotbox is heating tires to prep , and to keep your tires at even warm temp on those race days. Some folks use them to grow tires for stagger, if you heat a tire the air inside expands also makes the rubber softer. Rolling tires in the box you place your tires on a set of rollers which are very slowly turned by an electric rotisserie motor (similar to most high end barbeque grills). You typically place prep in a prep tray directly under the tires to prep them from the outside, or place prep inside of the wheel and tire assembly through the valve stem via a turkey baster or similar method, to "rotisserie" prep them from the inside out.
There are two main kinds of hotboxes out there, some you need to purchase a heat gun basically blow the heat in the box, this box is usually less expensive 300 - 500. The preferred box by most is a heat strip box, this box has a digital thermostat and you simply set your temp plug it in. Also has a prep pan in the bottom that is removable. However, these boxes are usually 700 +. You can check out the one we make by going to my facebook page https://www.facebook.com/josh.spicerenterprises. Hope this helps.